Preconditioning of hydroforming catalysts



naphthas. .phasized at the high treating temperatures normally re- United States Patent PRECONDI'TIQNING:QFJ'IYDROEQRMING CATALS 5 Walker F. Johnston, Jr.','I JafMarque','flex., assignor to The Am'eric'amOil' Company r w Appli ationN rembe ;29,; Serial N0.;4,71,,9'06

' This invention relates 'to the reforming '.of hydrocar- -bons. More particularly, it relates to the' hydroforrning elevated temperature and pressure in' the presence of .added hydrogen. Such. catalysts normally egrhibit a moreor less steady decline in activity, as 'evidenced by the octane number of the product, the rate, of de cl ine depending upon the process conditions, such as, temperature, hydrogen partial pressure, charging stock composition, and the presence and proportions of deleterious substances such as sulfur, arsenic, nitrogen,,and th'e'l'ilre 1n,the charging stock. The decline rate isespecially rapid in the platinum hydroforming of the so-called naphthenic 30 naphthas, i. e., naphthas containing. more than i50 p er- I cent naphthenes and. more than 70 percent. naphthenes plusaromatics. An object of my invention is toQprecondition a platinum-alumina catalyst in such a way. as to maintain its activity in the hydrofo'rming of naphthenic The observedadeactivation tends to be emquired to obtain premium gasolinesof F-l, octane number of 90 or higher, making it.correspondinglyfdifiicult to produce a refo-rrnate pool having an average octane numberof the desired level. Another object of my invention is to extend the effective cycle length of platinum alumina catalysts in the high-severity hydroforrning of naphthenic naphthas. A further object is to increase the refcrmate pool octane number obtainable with platinumalumina catalysts. These and other objectsof my invention will be apparent fromthe appended description and claims.

My invention is basically a method for,precon ditioning a platinum-alumina catalyst to render it less susceptible to deactivation by naphthenic naphthas during the hydroforming thereof. In accordance with ,my invention, a platinum-alumina catalyst is subjected to a preliminary contact under hydroforming conditions for a per-iod of to 200 hoursror more with a paralfinic naphtha i. e., a. naphtha containing more than about 30 percent paraflins and less than about 50 percent naphthenes. After the catalyst has beenpretreated inthis way, it -is capable octane numbers in the range of around 95 to. 105 The,

hydroforming process is ordinarily carried out at apressure within the range of about 100 to 1,000'pounds per square inch gage, a temperature between about 850 and -1000 F., and hourly weightspace velocity between about 0.5 and 5, and a hydrogen input rate between about 12,000

"Patein ted Jan. 13, 1959 .2 v and 10,000 .starrdard cubic feet per barrel .of. charging i s tock. ,Eor aupro-duct.octane level aboveaboutf95, the pressure should preferably" be between about Q1010 and ,.-500. .pounds. =per; sguare inch gage, theternperature be- 5 tweenabpnt925and.975 F., and the space velocity be- .twee neabout.0.5, and 2. Under the foregoing conditions, it iscommonly observed that the catalyst, declines inactivityat a,rate ;gr eater than 2 F-l octane numbers ge -1 0,0 l'lpurs if, the charging ,stock is a naphthenic 10 naphtha. I

ln conditioning a platinum-alumina catalyst for contact with such a chargingwstock, I..subject the catalyst to ,a preliminary treatment with a jparafiinic naphtha, prefl-erably. having an 1 SflM finalv boiling point below, about 4252-1 and ,a sulfur content-below about 0.05 weight- ,1) cent, at a temperature .between about 8 5O and 950 Iapress1ireibelow about 500 pounds per. square inch gag, .anda..weight hourlyspace velocity within the .iisuallhydrofogming rangeof about 0.5 to 5 for aperiod ound ,l0. hours o'rlrno're. I prefer to carryout the ;-pretreaj;ment:lfor a sufficient length of time. to reachQa lsubstantially.constant catalyst activity decline rate, op- -iemang; under. the, :hydroforming conditions thereafter to be employed, and for this purpose a pretr eat ing timelof around 25 to 100 hours is ordinarily sufiicient, depending upon the refractoriness of the stock employed in the By 'ie ar sc namea Ihav u d s a n efiecti ,a large decrease the activity decline rates of platinumalumina.catalysts when employed for the hydroforrning vof,naphthenic charging. stock's. After catalysts have. been .treated in this way, Iifind, that they commonly exhibit .amactivitydecline;ratev less than 1 F-rl. octane number -,per. ,l00, hours-. in the ensuing. hydroforrning operation. The extent of jimprovemen t in each case depends upon wthe degree of pretreatment and upon theseverity of 'deactivation ordinarily, produced by rthe naphthenic. stock.

1 -The;efiectivenessof my new technique is conveniently illustrated: in connection with. the hydroformingf of a Texas City naphthenic-.heavynaphtha, containing around 60 percent 'naphthenes and around80 percent naphthenes plus aromatics.- Such a: naphtha, :when hydroforrned under substantially isothermal conditions at 920 F., 3 00 pounds per square ,inch gage, 1.5 we ight hourly space velocity, and 5,000 standard cubic feet of hydrogen per barrel, ordinarily exhibitsanoctane. declinemate, of 10 :-F--1 unitspers 100 hours. :Whenthe catalyst is subjected to a pretreatment for 10 to .100 hours or moreunder, the

-sam'e conditionslrwith a TeXasCity paraffinic heavy naphtha containing around -40 percent of paraffins, the decline rate in the'subseouenthydroforming ofthe naphthenic heavy naphtha is reduced to less than 1 F-l unit per 100 hours. t

-;I am" uncertain as to the precise mechanism whereby the}advantageousresnlts of my preconditioning operation arefa chieved. My technique and; an equivalent of rea i n a i t a n .treet k i i e- QI I. i esr n fihe-mb m th ds. c mo mploye .fo ,roma ne.qqu miu tsf m P t um w ss n such methods do not .prod uce .the "improved cat lyst ,a tiv txm i ep nc .typic f my.. nv .n o seem .i e y,-,..i n .fact,,, het th jr l f' e y tpg so is ,notinvolved since I have suecessfullyremployed a paratfinic. naphtha lpretreatlngv stock which was somewhat higher'in sulfur content than the naphthenicQnaphtha subsequently processed. ,Whatever its. method ofaction, however, my, pretreating step .is;;effective in prolonging the useful cycle li-fe .of platinum alumina.catalystsl My invention 11 be ms-re fully;understood ,from the i l auin tqps e saws xn l N 3 Example 1 A Texas City naphthenic heavy naphtha having an ASTM boiling range of 258 to 402 F. and an API gravity of 45.7, and containing 20 volume-percent parafiins, 58 percent naphthenes, 22 percent aromatics, 0.015 weight-percent sulfur, and 7 parts per million nitrogen, was subjected to hydroforming under isothermal conditions in the presence of a 0.6 percent platinum-on-alumina catalyst at 923 F., 300 pounds per square inch gage, 1.5 hourly weight space velocity, and 5,000 standard cubic feet of added hydrogen per barrel. The resulting data showed an activity decline rate of 10 F-l units per 100 hours on stream.

In a comparative test, the catalyst was pretreated for 216 hours under the same conditions with a Texas City paraffinic heavy naphtha having a boiling range of 222 to 406 F. and an API gravity of 507, and containing 38 volume-percent paraffins, 1 percent olefins, 48 percent naphthenes, 13 percent aromatics, 0.035 weightpercent sulfur, and approximately 7 parts per million of nitrogen. At the end of this time, the flow of paraflinic naphtha was discontinued and the naphthenic naphtha was introduced and treated under the same process conditions. The reformate F-l octane rating decreased from 100.9 to 99.4 during the next 300 hours, correspond ing to an activity decline rate of only 0.5 F-1 unit per 100 hours on stream.

Example 2 A Texas City parafiinic heavy naphtha having a final boiling point of 437 F. and containing 38 percent paraf- -fins, 1 percent olefins, 48 percent napthtenes, and 13 percent aromatics, by volume, was subjected to reforming in'the presence of a 0.6 percent platinum-on-alumina catalyst at 300 pounds per square inch gage, 1.0 hourly weight space velocity, 927 F., and 5,000 standard cubic feet of hydrogen per barrel. The initial Fl octane number was 100.1 and the catalyst activity decline rate was 1.2 F'l units per 100 hours. At the end of 136 hours on stream, the charging stock was changed to a Texas City parafiinic heavy naphtha having a final boiling point of 442 F. No marked difference in results was noted between the two naphthas.

At the end of 184 hours on the paraffinic naphthas, the charging stock was changed to a Texas City naphthenic heavy naphtha having an ASTM final boiling point of 404 F. and containing 20 percent paraffins, 58 percent naphthenes, and 22 percent aromatics, by volume, together with 0.015 weight-percent sulfur. forming was continued under the same conditions, and a product was obtained during the 216-232 hour period having an F-l octane level of 101.3. The reformate octane number declined to 99.6 during the 376-392 hour period, corresponding to a decline rate of about 1.0 F-1 unit per 100 hours.

My new process is efiective for preconditioning alumina-supported platinum hydroforming catalysts in general, may types of which have been described in the prior art. It can be used, for example, in connection with unpromoted platinum-on-alumina, or with platinumalumina catalysts which include a promoting additive such as vanadia, chromia, titania, iridium, an oxide of phosphorus, or the like, or a mild cracking adjuvant, such as boria, silica, fluorine, chlorine, or the like. The catalysts commonly contain platinum in a proportion between about 0.05 and 1 percent by weight, based on dry A1 Promoters and other additives are usually employed in a proportion between about 0.1 and 8 percent by weight.

While I have described my invention with reference to certain specific embodiments thereof, it is to be understood that such embodiments are illustrative only and not by way of limitation. Numerous alternative charging stocks, catalysts, manipulative steps, and operating The hydroconditions will be apparent from the above description to those skilled in the art.

In accordance with the foregoing description, I claim as my invention:

1. In a method for hydroforming a naphthenic petroleum naphtha containing above about 50 percent naphthenes and above about 70 percent naphthenes and aromatics in the presence of an-alumina-supported platinum catalyst at a hydroforming temperature between about 850 and 1000 F. and obtaining therefrom a gasoline having an F-l octane number above about 90, in which operation the activity of said catalyst ordinarily declines at a rate greater than about 2 F-l units per 100 hours, the improvement which comprises preconditioning said catalyst prior to said hydroforming operation by exposing said catalyst when fully active to contact under hydroforming conditions with a paraflinic petroleum naphtha containing above about 30 percent parafiins and less than about 50 percent naphthenes for a period of time between about 10 and 200 hours, whereby the rate of decline in activity of the said catalyst in the ensuing hydroforming operation is reduced to less than about 1 F-l octane unit per 100 hours.

2. In a method for hydroforming a naphthenic petroleum naphtha containing above about 50 percent naphthenes and above about 70 percent naphthenes and aromatics in the presence of an alumina-supported platinum catalyst at a hydroforming temperature between about 850 and 1000 F. and a pressure between about 100 and 500 pounds per square inch gage and obtaining therefrom a gasoline having an F-l octane number between about and 105, in which operation-the activity of said catalyst ordinarily declines at a rate greater than about 2 F-l units per hours, the improvement which comprises preconditioning said catalyst prior to said hydroforming operation by exposing said catalyst when fully active to contact under hydroforming conditions with a parafiinic petroleum naphtha containing above about 30 percent parafiins and less than about 50 percent naphthenes for a period of time between about 10 and 200 hours, whereby the rate of decline in activity of said catalyst in the ensuing hydroforming operation is reduced to less than about 1 F-1 octane unit per 100 hours.

3. In a method for hydroforming a naphthenic petroleum naphtha containing above about 50 percent naphthenes and above about 70 percent naphthenes and aromatics in the presence of a fixed-bed catalyst consisting essentially of alumina and between about 0.05 and 1 percent by weight of platinum, based on dry A1 0 at a pressure between about 100 and 500 pounds per square inch gage and a hydroforming temperature between about 850 and 1000 F. sufficient to obtain therefrom a gasoline having an F-l' octane number between about 95 and 105, whereby the activity of said catalyst ordinarily declines at a rate greater than about 2 F-l octane units per 100 hours, the improvement which comprises preconditioning said catalyst prior to saidhydroforming operation by exposing said catalyst when fully active for a period of between about 25 and 100 hours to contact under hydroforming conditions with a parafiinic petroleum naphtha containing above about 30 percent parafiins, less than about 50 percent naphthenes, and less than about 0.05 percent sulfur, whereby the rate of decline in activity of said catalyst in the ensuing hydroforming operation is reduced to less than about 1 F-1 octane unit per 100 hours. 

1. IN A METHOD FOR HYDROFORMING A NAPHTHENIC PETROLEUM NAPHTA CONTAINING ABOVE ABOUT 50 PERSENT NAPHTHENES AND ABOVE ABOUT 70 PERCENT NAPHTHENES AND AROMATICS IN THE PRESENCE OF AN ALUMINA-SUPPORTED PLATINUM CATALYST AT A HYDROFORMING TEMPERATURE BETWEEN ABOUT 850 AND 1000* F. AND OBTAINING THEREFROM A GASOLINE HAVING AN F-1 OCTANE NUMBER ABOVE 90, IN WHICH OPERATION THE ACTIVITY OF SAID CATALYST ORDINARILY DECLINES AT A RATE GREATER THAN ABOUT 2 F-1 UNITS PER 100 HOURS, THE IMPROVEMENT WHICH COMPRISES PRECONDITIONING SAID CATALYST PRIOR TO SAID HYDROFORMING OPERATION BY EXPOSING SAID CATALYST WHEN FULLY ACTIVE TO CONTACT UNDER HYDROFORMING CONDITIONS WITH A PARAFFINIC PETROLEUM NAPHTHA CONTAINING ABOVE ABOUT 30 PERCENT PARAFFINS AND LESS THAN ABOUT 50 PERCENT NAPHTHENES FOR A PERIOD OF TIME BETWEEN ABOUT 10 AND 200 HOURS, WHEREBY THE RATE OF DECLINE IN ACTIVITY OF THE SAID CATALYST IN THE ENSUING HYDROFORMING OPERATION IS REDUCED TO LESS THAN ABOUT 1 F-1 OCTANE UNIT PER 100 HOURS. 